JP4923533B2 - Optical multilayer film, optical element, reflection mirror and projector - Google Patents

Description

  The present invention relates to an optical multilayer film, an optical element, a reflection mirror, and a projector.

Conventionally, an optical multilayer film that selectively reflects light of a specific wavelength is mounted on various optical devices. For example, such an optical multilayer film is used for a color synthesizing optical element (cross dichroic prism) or a reflection mirror (notch filter) of a projector.
More specifically, as shown in FIG. 36, the projector 4 ′ includes an illumination optical device 41 including a light source device 411, and a color separation optical device 42 that separates a light beam emitted from the light source device 411 into three color lights. ', A light modulation device (liquid crystal panel 441) that modulates each color light according to image information, and a color combining optical element (cross dichroic prism 444') that combines the light modulated by the light modulation device to form an optical image. And a projection optical device (projection lens 45) for enlarging and projecting an optical image.

The illumination optical device 41 includes a light beam splitting optical element (first lens array 412) and a condensing element (second lens array 413 and superimposing lens 415), and the light beam splitting optical element is emitted from the light source device 411. Are divided into a plurality of partial light beams, and each partial light beam is superposed on the image forming area of the light modulation device (liquid crystal panel 441) by a condensing element.
Reference numeral 414 denotes a polarization conversion element that is disposed between the second lens array 413 and the superimposing lens 415 and converts light from the second lens array 413 into substantially one type of polarized light.

The color separation optical device 42 ′ includes a dichroic mirror 421 ′ that transmits red light and green light and reflects blue light, and a dichroic mirror 422 ′ that transmits red light and reflects green light. The emitted light beam is separated into red light, green light, and blue light.
Each separated color light is incident on a liquid crystal panel 441 (441R, 441G, 441B) installed in accordance with each color light via a field lens 418 and an incident side polarizing plate 442.
The red light is guided to the liquid crystal panel 441 (441R) for red light by the relay optical system 43 including the incident side lens 431, the relay lens 433, and the reflection mirrors 432 and 434.

In the liquid crystal panel 441, light modulation is performed according to image information, and the light beam subjected to the light modulation is incident on the cross dichroic prism 444 ′ via the exit-side polarizing plate 443.
The cross dichroic prism 444 ′ includes four optical multilayer films that reflect red light and transmit blue light and green light, and four optical multilayer films that reflect blue light and transmit red light and green light. It is provided in a substantially X shape along the interface of the triangular prism, and three color lights are synthesized by these optical multilayer films.
The color image emitted from the cross dichroic prism 444 ′ is enlarged and projected by the projection lens 45 to form a large screen image on a screen (not shown).

Here, in the conventional projector 4 ′, since the relay optical system 43 is installed in the optical path of red light (wavelength region: about 640 to 810 nm), the optical path from the light source device 411 to the liquid crystal panel 441R is changed to other color light. Longer than that. Therefore, there is a problem that the loss of light amount of red light (wavelength region: about 640 to 810 nm) is increased, and the balance with other color lights is deteriorated.
Therefore, a method has been proposed in which green light (wavelength region: about 500 to 560 nm) with the largest amount of light is introduced into the relay optical system 43 to adjust the balance with other color lights (for example, see Patent Document 1).

Here, when green light (wavelength region: about 500 to 560 nm) with the largest amount of light is introduced into the relay optical system, the green light is selectively reflected, and blue light (wavelength region: about 430 to 500 nm) and An optical multilayer film that transmits red light (wavelength region: about 640 to 810 nm) needs to be used for the color synthesis optical element.
However, development of an optical multilayer film having a low transmittance for green light and a high transmittance for blue light and red light has not progressed, and development of an optical multilayer film having such optical characteristics is strongly desired.

  On the other hand, the luminous flux emitted from the light source device 411 includes yellow light at 560 to 600 nm, which is a substantially intermediate wavelength between red light and green light. When such yellow light enters the liquid crystal panel 441 (441R) for red light together with red light and is projected onto the screen, the projected image that should originally be red becomes orange, and the yellow light Is incident on the liquid crystal panel 441 (441G) for green light together with the green light and projected onto the screen, the projected image that should be green may become yellowish green. As a result, the color reproducibility and contrast of the projected image projected by the projector 4 'may be reduced.

In order to solve such a problem, for example, on the optical path between the light source device 411 and the first lens array 412, a reflection mirror 419 ′ that removes yellow light having a wavelength of about 580 nm from the light beam emitted from the light source device 411. A configuration in which a notch filter is provided is known (see, for example, Patent Document 2). However, this Patent Document 2 does not disclose a specific configuration of the notch filter, and in reality, there is a possibility that a reduction in contrast cannot be prevented.
For this reason, there is a need for a reflection mirror including an optical multilayer film that reliably reflects yellow light in a narrow band having a wavelength region of about 560 to 590 nm and reliably transmits blue light, green light, and red light. .

Japanese Patent No. 3254680 (5th page, FIG. 1) Japanese Patent Application Laid-Open No. 11-249098 (page 4, FIG. 1)

  As described above, in the projector, an optical multilayer film capable of reflecting green light and transmitting blue light and red light with a color synthesizing optical element (cross dichroic prism 444 ′) is required, and a reflection mirror 419 is required. There is a demand for an optical multilayer film that can reflect yellow light and transmit blue light, green light, and red light by '(notch filter). That is, there is a demand for an optical multilayer film that can selectively reflect green light and yellow light according to the purpose of use, and can transmit blue light and red light with high transmittance.

  In view of the above-described problems, an object of the present invention is an optical multilayer that can selectively reflect light of a predetermined wavelength according to the purpose of use, and can transmit blue light and red light with high transmittance. It is to provide a film, an optical element, a reflection mirror and a projector.

  The optical multilayer film of the present invention is an optical multilayer film in which a high refractive index layer and a low refractive index layer having different refractive indexes are alternately laminated, and the optical multilayer film includes a high refractive index layer and an optical film thickness different from each other. In order to prevent undulation of transmission loss of transmitted light beams of red light and blue light on a repeating layer in which low refractive index layers are alternately laminated and at least one of a light beam incident side and a light beam emitting side of the repeating layer And a matching layer in which one or more high refractive index layers and low refractive index layers are alternately laminated, and the repeating layer is 3.0 ≦ (high refractive index layer in the repeating layer) ) / (Sum of optical film thicknesses of low refractive index layers in the repetitive layer) ≦ 30.

According to the present invention, the high refractive index layer and the low refractive index layer are alternately arranged in the repeating layer, and the optical film thickness of each of the high refractive index layer and the low refractive index layer in the repeating layer is further increased. By setting the ratio to 3.0 or more and 30 or less, the wavelength region of light reflected by the optical multilayer film can be set within a range of about 500 nm or more and 600 nm or less. That is, for example, if the ratio of the film thickness is set to 3.0 or more and 6.0 or less, the transmittance of broadband green light (wavelength region: about 500 to 600 nm) can be reduced to about 0%. If the thickness ratio is set to 10 or more and 30 or less, the transmittance of narrow-band yellow light (wavelength region: about 560 to 600 nm) can be made substantially 0%. In addition, the optical multilayer film has a ratio of the film thickness of 3.0 to 30 in any ratio, blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 to 640). 810 nm) with a transmittance of approximately 100%.
Therefore, the optical multilayer film selectively reflects green light or yellow light and reliably transmits blue light and red light by adjusting the ratio of the film thickness. An optical multilayer film according to the purpose of use such as application to a cross dichroic prism or a reflection mirror can be obtained. In addition, since the reflection region in the optical multilayer film can be arbitrarily changed simply by adjusting the ratio in the optical multilayer film, products corresponding to various applications can be manufactured using the same optical multilayer film manufacturing apparatus.

When (total of optical film thickness of high refractive index layer in repeating layer) / (total of optical film thickness of low refractive index layer in repeating layer) is less than 3.0, the reflected light There is a possibility that the wavelength region becomes wider and the transmittance of red light is lowered. On the other hand, when (total of optical film thickness of high refractive index layer in repeating layer) / (total of optical film thickness of low refractive index layer in repeating layer) exceeds 30, the reflectivity decreases. In addition, the undulation (ripple) of transmission loss of red light and blue light may increase.
In addition, since the optical multilayer film of the present invention includes a matching layer on at least one of the light beam incident side and the light beam emission side, it is possible to reduce the undulation (ripple) of transmission loss of red light and blue light. .

In the present invention, in the repeating layer, it is preferable that the optical film thickness of the high refractive index layer decreases toward the center of the thickness width of the repeating layer, and the optical film thickness of the low refractive index layer increases.
Thus, while maintaining 3.0 ≦ (total optical film thickness of the high refractive index layer in the repeating layer) / (total optical film thickness of the low refractive index layer in the repeating layer) ≦ 30, the repeating layer By reducing the optical film thickness of the high refractive index layer and increasing the optical film thickness of the low refractive index layer toward the center of the thickness width (intermediate point from the light beam entrance side and light beam exit side of the repeating layer) Further, ripples (transmission fluctuations) of red light and blue light can be prevented, and the transmittances of red light and blue light can be reliably increased.
In order to reliably prevent red light and blue light ripples (transmission fluctuations), there is a method of increasing the number of high refractive index layers and low refractive index layers of the matching layer. There is a possibility that the number of films to be formed increases and the manufacturing efficiency of the optical multilayer film is lowered.
In the present invention, by adjusting the optical film thickness of the high-refractive index layer and the optical film thickness of the low-refractive index layer in the repeating layer, ripples of red light and blue light (transmission fluctuation) can be prevented. Therefore, it is not necessary to increase the number of matching layer films, and a decrease in the manufacturing efficiency of the optical multilayer film can be prevented.

In the present invention, the repeating layer is 3.0 ≦ (total optical film thickness of the high refractive index layer in the repeating layer) / (total optical film thickness of the low refractive index layer in the repeating layer) ≦ 6. 0.0 is preferred.
Thus, (total sum of optical film thickness of high refractive index layer in repeating layer) / (total sum of optical film thickness of low refractive index layer in repeating layer) is set to 3.0 or more and 6.0 or less. The wavelength region of light reflected by the optical multilayer film can be 500 nm or more and 600 nm or less, and broadband green light can be reliably reflected. In addition, by setting (total of optical film thickness of high refractive index layer in repeating layer) / (total of optical film thickness of low refractive index layer in repeating layer) to 3.0 or more and 6.0 or less, blue An optical multilayer film capable of transmitting light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 to 810 nm) with high transmittance can be obtained.
When (total of optical film thickness of high refractive index layer in repeating layer) / (total of optical film thickness of low refractive index layer in repeating layer) is less than 3.0, the reflected light There is a possibility that the wavelength region becomes wider and the transmittance of red light is lowered. In addition, when (total of optical film thickness of high refractive index layer in repeating layer) / (total of optical film thickness of low refractive index layer in repeating layer) exceeds 6.0, reflection is performed. Since the wavelength region of light becomes narrow, it becomes difficult to reliably reflect green light.
Therefore, for example, when such an optical multilayer film of the present invention is used for a color synthesis optical element of a projector, green light (wavelength region: about 500 to 560 nm) with the largest amount of light can be selectively reflected, and blue Light (wavelength region: about 430 to 500 nm) and red light with a large light loss (wavelength region: about 640 to 810 nm) can be transmitted with high efficiency.

In the present invention, the number of high refractive index layers and low refractive index layers in the repeating layer is preferably 8 or more.
If the number of films constituting the repetitive layer is less than 8, respectively, the green light transmittance increases, and there is a possibility that the green light cannot be reliably reflected.
On the other hand, in the present invention, since the number of high refractive index layers and low refractive index layers constituting the repeating layer is 8 or more, such a problem does not occur.

Furthermore, in the present invention, the high refractive index layer forming the repeating layer and the matching layer contains Ta ₂ O ₅ , and the low refractive index layer contains SiO _2. preferable.
By using Ta ₂ O ₅ for the high refractive index layer, blue light can be prevented from being absorbed by the high refractive index layer.
Further, by using SiO ₂ for the low refractive index layer, the cost of the low refractive index layer can be reduced.

On the other hand, in the present invention, the repeating layer has 10 ≦ (total optical film thickness of the high refractive index layer in the repeating layer) / (total optical film thickness of the low refractive index layer in the repeating layer) ≦ 30. It is preferable that
According to the present invention, (the sum of the optical film thicknesses of the high refractive index layers in the repeating layer) / (the sum of the optical film thicknesses of the low refractive index layers in the repeating layer) is set to 10 or more and 30 or less. Thus, the wavelength region of the light reflected by the optical multilayer film can be set to about 560 nm or more and 600 nm or less, and the narrow-band yellow light can be reliably reflected. Moreover, blue light (wavelength region) can be obtained by setting (total sum of optical film thickness of high refractive index layer in repeating layer) / (total optical film thickness of low refractive index layer in repeating layer) to 10 or more and 30 or less. : About 430 to 500 nm), green light (wavelength region: about 500 to 560 nm) and red light (wavelength region: about 640 to 810 nm) can be transmitted with high transmittance.
When (total of optical film thickness of high refractive index layer in repeating layer) / (total of optical film thickness of low refractive index layer in repeating layer) is less than 10, the reflection region is green light ( (Wavelength region: about 500 to 560 nm), and there is a possibility that the necessary amount of green light cannot be secured. On the other hand, when (total of optical film thickness of high refractive index layer in repeating layer) / (total of optical film thickness of low refractive index layer in repeating layer) exceeds 30, the specific wavelength of There is a possibility that the transmittance in light is improved and cannot be reflected well, and the undulation (ripple) of transmission loss of red light and blue light may be increased.
Therefore, for example, when such an optical multilayer film of the present invention is used for a reflection mirror of a projector, it is possible to reliably reflect narrow band yellow light (wavelength region: about 560 to 600 nm) and blue light (wavelength region). : About 430 to 500 nm), green light (wavelength region: about 500 to 560 nm) and red light (wavelength region: about 640 to 810 nm) can be transmitted with high efficiency, so that yellow light is emitted from green light and red light. Mixing can be prevented, and color reproducibility and image contrast can be improved.

In the present invention, the number of high refractive index layers and low refractive index layers in the repeating layer is preferably 15 or more.
If the number of films constituting the repetitive layer is less than 15, respectively, the transmittance of yellow light increases, and there is a possibility that yellow light cannot be reliably reflected.
In contrast, in the present invention, since the number of high refractive index layers and low refractive index layers constituting the repeating layer is 15 or more, such a problem does not occur.

In the present invention, in the repetitive layer, 1 / 4λ (λ = 430 nm) is defined as 1, and the total of the optical film thickness of the high refractive index layer and the optical film thickness of the low refractive index layer adjacent to each other. Is preferably set to about 4.0.
According to the present invention, the number of repeating layers can be kept to the minimum necessary level, and the transmission of blue light (wavelength region: about 430 to 500 nm) can be prevented from being inhibited.
Here, the total thickness is 2.0 (0.5λ), 4.0 (1λ), 6.0 (1.5λ). . . . If so, the reflectance at λ can be increased. Among these, when the total film thickness is 2.0 (0.5λ), the ratio of (total optical film thickness of high refractive index layer H) / (total optical film thickness of low refractive index layer L) Therefore, it is difficult to increase the reflectivity unless the number of layers in the repeated layer is significantly increased to about twice. Furthermore, the optical film thickness of the low refractive index layer L of the repeating layer becomes extremely thin, and it becomes difficult to form a uniform optical thin film. Further, when the total film thickness is 6.0 (1.5λ), the reflection band (band where the transmittance is approximately 0%) in the wavelength region of about 560 to 600 nm (yellow light), and the reflection band However, the reflection band adjacent to the short wavelength side is too close, and transmission of blue light (wavelength region: about 430 to 500 nm) is inhibited. On the other hand, if the total film thickness is set to about 4.0, the number of repeating layers can be kept to the minimum necessary level, and the transmission of blue light can be prevented from being inhibited.

Furthermore, in the present invention, the repetitive layer is disposed on at least one of the light beam entrance side and the light beam exit side in order to reduce the transmitted light amount of blue light and green light in the transmitted light beam. It is preferable to have a light reducing layer in which one or more refractive index layers are alternately stacked.
According to the present invention, the optical multilayer film can reflect yellow light in a narrow band (wavelength region: about 560 to 590 nm) and transmit red light (wavelength region: about 640 to 810 nm) with high transmittance. Can be made. Furthermore, blue light (wavelength region: about 430 to 500 nm) and green light (wavelength region: about 500 to 560 nm) can be attenuated and transmitted with an arbitrary transmittance. For this reason, a single optical multilayer film functions as a reflecting mirror that reflects yellow light and transmits blue light, green light, and red light, and reduces blue light and green light at an arbitrary transmittance. Two functions, that is, a function as an ND (Neutral Density) filter to be transmitted, can be expressed. And if the optical film thickness of each of the high refractive index layer and the low refractive index layer of the dimming layer is appropriately adjusted, the transmittance of blue light and green light can be arbitrarily set, so that it can be easily and according to the purpose of use. The light amount can be suitably adjusted.

In the present invention, it is preferable that the high refractive index layer contains Nb ₂ O ₅ and the low refractive index layer contains SiO ₂ .
According to the present invention, by using Nb ₂ O ₅ for the high refractive index layer, it is possible to suppress the blue light from being absorbed by the high refractive index layer.
Further, by using SiO ₂ for the low refractive index layer, the cost of the low refractive index layer can be reduced.

An optical element of the present invention includes the optical multilayer film according to any one of claims 1 to 5.
According to the present invention, since any one of the optical multilayer films described above is provided, an optical element that can reflect green light and transmit blue light and red light can be obtained.

Examples of the optical element include a color combining optical element that combines incident red light, blue light, and green light and emits the light in a predetermined direction.
The color synthesizing optical element includes four triangular prisms each having two substantially orthogonal side surfaces, and a prism assembly formed by bonding the two side surfaces of each triangular prism to each other, and the prism assembly A pair of optical multilayer films formed between the triangular prisms adjacent to each other, and one of the pair of optical multilayer films reflects green light, and red and blue light. The optical multilayer film described above that transmits light, and the other optical multilayer film reflects either red light or blue light and transmits either red light or blue light and green light. It is another optical multilayer film.
Since such a color synthesis optical element has any of the optical multilayer films described above, it can reflect green light and transmit blue light and red light, and can balance green light, blue light, and red light in a well-balanced manner. Can be synthesized.

Further, the projector of the present invention includes a plurality of light modulation devices that modulate the light beam emitted from the light source according to image information for each color light, a color combining optical element that combines the light beams modulated by each light modulation device, A projector comprising a projection optical device that enlarges and projects the color light synthesized by the color synthesis optical element to form a projection image, and the color synthesis optical element is the color synthesis optical element described above.
Since such a projector has the above-described color combining optical element, green light, blue light, and red light can be combined with good balance, and a projection image with good color balance can be formed.

On the other hand, the reflection mirror of the present invention is provided on the transparent substrate having a flat plate shape, reflects yellow light from an incident light beam, and transmits blue light, green light, and red light. And an optical multilayer film.
According to such a reflecting mirror, the optical multilayer film reflects yellow light (wavelength region: about 560 to 600 nm), blue light (wavelength region: about 430 to 500 nm), green light (wavelength region: about 500 to 560 nm) and red light (wavelength region: about 640 to 810 nm) can be transmitted with high efficiency, so that yellow light can be prevented from being mixed into red light or green light in the transmitted light. For this reason, for example, when the above-described reflection mirror is applied to a projector, yellow light can be removed from the light flux from the light source device, so that the color reproducibility and contrast of the projected image can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[1. Configuration of optical multilayer film 1]
FIG. 1 shows a schematic diagram of an optical multilayer film according to the present invention. FIG. 2 shows the optical film thickness of the high refractive index layer and the optical film thickness of the low refractive index layer in the optical multilayer film.
The numbers on the horizontal axis in FIG. 2 indicate the first layer to the 28th layer, and the vertical axis indicates the optical film thickness when 1 / 4λ (λ = 430 nm) is defined as 1.
The optical multilayer film 1 reflects broadband green light (wavelength region: about 500 to 600 nm) and transmits blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 nm to 810 nm). It is a membrane.
As shown in FIG. 1, the optical multilayer film 1 is a film in which high refractive index layers H and low refractive index layers L are alternately stacked. The total number of low-refractive index layers L and high-refractive index layers H of the optical multilayer film 1 is, for example, 28 layers, 14 layers each.
Examples of the material for the low refractive index layer L include SiO ₂ and MgF ₂ , and the refractive index ranges from 1.38 to 1.46.
Examples of the material of the high refractive index layer H include Ta ₂ O ₅ , TiO ₂ , ZrO _{2, and the} like, and the refractive index ranges from 2.0 to 2.5.
Among these, it is preferable to use SiO ₂ as the material for the low refractive index layer L and Ta ₂ O ₅ as the material for the high refractive index layer H.
Such an optical multilayer film 1 includes a pair of matching layers 11 and a repeating layer 12 disposed between the pair of matching layers 11.

(1-1. Configuration of matching layer)
The matching layer 11 is a layer provided to prevent fluctuations (ripples) in the transmittance of light beams (red light and blue light) transmitted through the optical multilayer film 1.
The matching layer 11 is a layer provided on each of the light incident side and the light exit side of the optical multilayer film 1. In this embodiment, the matching layer 11 includes two low-refractive index layers L and two high-refractive index layers H. Are alternately stacked. In other words, one matching layer 11 is formed from the first layer to the fourth layer of the optical multilayer film 1, and the other matching layer 11 is formed from the 25th layer to the 28th layer.

The matching layer 11 includes a first matching portion 111 positioned on the outermost side (light beam emission side or light beam incident side) of the optical multilayer film 1 and a second matching portion positioned inside the first matching portion 111. 112.
The first matching portion 111 has one high refractive index layer H and one low refractive index layer L. As shown in FIG. 2, the relationship between the optical film thickness of the low refractive index layer L and the optical film thickness of the high refractive index layer H in the first matching section 111 is 1 ≦ (optical film of the high refractive index layer H). Thickness) / (Optical film thickness of the low refractive index layer L) ≦ 2.
When 1 / 4λ (λ = 430 nm) is defined as 1, the optical film thickness of the low refractive index layer L is, for example, 0.5 or less, and the optical film thickness of the high refractive index layer H is, for example, 0.7 or less.

The second matching section 112 has one high refractive index layer H and one low refractive index layer L, and light between the first matching section 111 and the repeating layer 12 described later. It is a layer provided in order to suppress reflection of light.
The optical film thickness of the high refractive index layer H of the second matching part 112 is the most in the optical film thickness of the high refractive index layer H of the first matching part 111 and the second matching part 112 of the repeating layer 12 described later. It is preferable that it is a dimension between the optical film thickness of the near high refractive index layer H.
Similarly, the optical thickness of the low refractive index layer L of the second matching portion 112 is equal to the optical thickness of the low refractive index layer L of the first matching portion 111 and the second matching portion of the repeating layer 12 described later. It is preferable that the size be between the optical film thickness of the low refractive index layer L closest to 112.
In the present embodiment, when 1 / 4λ (λ = 430 nm) is defined as 1, the optical film thickness of the high refractive index layer H in the second matching portion 112 is, for example, about 4.0, and low refractive index. The optical film thickness of the rate layer L is about 0.36 (see FIG. 2).

(1-2. Configuration of repeating layer)
The repeating layer 12 is disposed between the pair of matching layers 11 and reflects broadband green light (wavelength region: about 500 to 600 nm), as well as blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region). : About 640 nm to 810 nm) with a transmittance of about 100%. The repeating layer 12 is formed by alternately laminating a high refractive index layer H and a low refractive index layer L, and the high refractive index layer H and the low refractive index layer L are 8 layers or more and 15 layers or less, respectively. It is preferable.
In the present embodiment, the repeating layer 12 is a layer composed of the fifth to 24th layers of the optical multilayer film 1, and the high refractive index layer H and the low refractive index layer L in the repeating layer 12 are each 10 layers. is there.
In the repeating layer 12, the optical film thickness of the high refractive index layer H and the optical film thickness of the low refractive index layer L are different. For example, the optical film thickness of the high refractive index layer H in the repeating layer 12 is 5.1 or more and 5.6 or less, and the optical film thickness of the low refractive index layer L in the repeating layer 12 is 0.4 or more and 1.0. It is as follows.

In such a repeating layer 12, the relationship between the optical film thickness of the high refractive index layer H and the optical film thickness of the low refractive index layer L is 3.0 ≦ (the total optical film thickness of the high refractive index layer H). / (Total optical film thickness of the low refractive index layer L) ≦ 6.0.
Here, when Ta ₂ O ₅ is used as the material of the high refractive index layer H and SiO ₂ is used as the material of the low refractive index layer L, 4.0 ≦ (Optical of the high refractive index layer H) It is preferable that the sum of the film thicknesses) / (the sum of the optical film thicknesses of the low refractive index layer L) ≦ 5.0.
Further, when ZrO ₂ is used as the material of the high refractive index layer H and SiO ₂ is used as the material of the low refractive index layer L, 3.0 ≦ (the optical film thickness of the high refractive index layer H It is preferable that (sum) / (sum of optical film thicknesses of low refractive index layer L) ≦ 5.0.
Further, when TiO ₂ is used as the material of the high refractive index layer H and SiO ₂ is used as the material of the low refractive index layer L, 4.0 ≦ (the optical film thickness of the high refractive index layer H It is preferable that (sum) / (sum of optical film thicknesses of the low refractive index layer L) ≦ 6.0.

Further, in the repeating layer 12, the optical film thickness of the high refractive index layer H becomes thinner toward the center of the thickness width of the repeating layer 12, and the optical film thickness of the low refractive index layer L is equal to the thickness width of the repeating layer 12. Thick toward the center.
For example, in the repetitive layer 12, (optical film thickness of the high refractive index layer H) / (optical film thickness of the low refractive index layer L) is 6 in the vicinity of the portion adjacent to the second matching portion 112 of the matching layer 11. In the central portion of the thickness width of the repeating layer 12, (optical film thickness of the high refractive index layer H) / (optical film thickness of the low refractive index layer L) is about 5.0. That is, the value of (optical film thickness of the high refractive index layer H) / (optical film thickness of the low refractive index layer L) is determined from the vicinity of the portion adjacent to the second matching portion 112 of the matching layer 11 of the repeating layer 12. It gradually decreases toward the center of the thickness width.

The relationship between the light transmittance of the optical multilayer film 1 and the wavelength region of the light flux is as shown in FIG.
In FIG. 3, the transmittance of blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 nm to 810 nm) is approximately 100%, and the transmittance of green light (wavelength region: about 500 to 600 nm). Is approximately 0%. And the fluctuation | variation (ripple) of the transmittance | permeability of blue light and red light is small.

[2. Configuration of optical multilayer film 3]
FIG. 4 shows a schematic diagram of an optical multilayer film according to the present invention. FIG. 5 shows the optical film thickness of the high refractive index layer and the optical film thickness of the low refractive index layer in the optical multilayer film. The numbers on the horizontal axis in FIG. 5 indicate the first layer to the 44th layer, and the vertical axis indicates the optical film thickness when 1 / 4λ (λ = 430 nm) is defined as 1.
The optical multilayer film 3 is formed on a flat transparent substrate such as a glass plate, for example, and reflects a narrow-band yellow light (wavelength region: about 560 to 600 nm: wavelength width: about 30 to 40 nm) and red. Light (wavelength region: about 640 nm to 810 nm) is transmitted with high transmittance. In addition, the optical multilayer film 3 can transmit blue light (wavelength region: about 430 to 500 nm) and green light (wavelength region: about 500 to 560 nm) by reducing the light with an arbitrary transmittance. .

As shown in FIG. 4, the optical multilayer film 3 is a film in which high refractive index layers H and low refractive index layers L are alternately stacked. The total number of low refractive index layers L and high refractive index layers H of the optical multilayer film 3 is, for example, 44 layers.
As the material of the low refractive index layer _L, SiO 2, MgF ₂ or the like can be exemplified, the range of refractive index is 1.38 to 1.46.
Examples of the material of the high refractive index layer H include Nb ₂ O ₅ , Ta ₂ O ₅ , TiO ₂ , ZrO _{2 and the} like, and the range of these refractive indexes is in the range of 2.0 to 2.5.
Among these, it is preferable to use SiO ₂ as the material for the low refractive index layer L and Nb ₂ O ₅ as the material for the high refractive index layer H.

  Such an optical multilayer film 3 is configured by laminating a matching layer 31, a repeating layer 32, and a light reducing layer 33 in this order. In this embodiment, as shown in FIGS. 4 and 5, the matching layer 31 corresponds to the first to fourth layers, the repeating layer 32 corresponds to the fifth to 38th layers, and the dimming layer. 33 corresponds to the 39th to 44th layers.

  The matching layer 31 is a layer provided to prevent fluctuation (ripple) in the transmittance of the light beam (red light and blue light) transmitted through the optical multilayer film 3. Provided on the side. In the present embodiment, as shown in FIG. 4, the matching layer 31 is provided as one layer on the light incident side of the optical multilayer film 3, and the first matching portion 311 located on the outermost side of the optical multilayer film 3. And a second matching portion 312 located inside the first matching portion 311. The first matching portion 311 and the second matching portion 312 have substantially the same configuration as the first matching portion 111 and the second matching portion 112 in the optical multilayer film 1 described above. Omitted.

  The repeating layer 32 reflects yellow light (wavelength region: about 560 to 600 nm), blue light (wavelength region: about 430 to 500 nm), green light (wavelength region: about 500 to 560 nm), and red light ( (Wavelength region: about 640 nm to 810 nm). The repetitive layer 32 is formed by alternately stacking a high refractive index layer H and a low refractive index layer L. The high refractive index layer H and the low refractive index layer L are 15 layers or more and 50 layers or less, respectively. The number of layers is preferably 15 or more and 30 or less.

In such a repeating layer 32, the relationship between the optical film thickness of the high refractive index layer H and the optical film thickness of the low refractive index layer L is 10 ≦ (total optical film thickness of the high refractive index layer H) / ( The total optical film thickness of the low refractive index layer L) is preferably set to ≦ 30.
Here, when Nb ₂ O ₅ is used as the material of the high refractive index layer H and SiO ₂ is used as the material of the low refractive index layer L, 15 ≦ (optical film thickness of the high refractive index layer H) ) / (Total optical film thickness of the low refractive index layer L) ≦ 25.
When Ta ₂ O ₅ is used as the material of the high refractive index layer H and SiO ₂ is used as the material of the low refractive index layer L, 13 ≦ (the optical film thickness of the high refractive index layer H It is preferable that (sum) / (sum of optical film thicknesses of low refractive index layer L) ≦ 23.
When ZrO ₂ is used as the material for the high refractive index layer H and SiO ₂ is used as the material for the low refractive index layer L, 12 ≦ (total optical film thickness of the high refractive index layer H) / (Total optical film thickness of low refractive index layer L) ≦ 22 is preferable.
Further, when TiO ₂ is used as the material of the high refractive index layer H and SiO ₂ is used as the material of the low refractive index layer L, 17 ≦ (total optical film thickness of the high refractive index layer H) / (Total optical film thickness of the low refractive index layer L) ≦ 27 is preferable.

In the repeating layer 32, the optical film thickness of the high refractive index layer H becomes thinner toward the center of the thickness width of the repeating layer 32, and the optical film thickness of the low refractive index layer L is equal to the thickness width of the repeating layer 32. Thick toward the center.
For example, in the film configuration of FIG. 5, the end of the repetitive layer 32 in the thickness direction, that is, the high refractive index layer H of the fifth layer and the low refractive index layer L of the sixth layer (high refractive index). The optical thickness of the refractive index layer H) / (the optical thickness of the low refractive index layer L) is about 26.5, and the central portion of the thickness width of the repeating layer 32, that is, the 21st high refractive index layer H And the 22nd low refractive index layer L, (optical film thickness of the high refractive index layer H) / (optical film thickness of the low refractive index layer L) is about 15.3. That is, in the repeating layer 32, the value of (optical film thickness of the high refractive index layer H) / (optical film thickness of the low refractive index layer L) is equal to both ends in the thickness width direction adjacent to the matching layer 31 and the light attenuation layer 33. It decreases in a quadratic function from the part side toward the central part.

In the repeating layer 32, the optical film thickness of the high refractive index layer H and the optical film thickness of the low refractive index layer L are different. For example, the optical film thickness of the high refractive index layer H in the repeating layer 32 is 3.6 or more and 3.8 or less, and the optical film thickness of the low refractive index layer L in the repeating layer 32 is 0.2 or more and 0.4. It is as follows. In this case, in the repeating layer 32, 1 / 4λ (λ = 430 nm) is defined as 1, and the total of the optical film thickness of the high refractive index layer H and the optical film thickness of the low refractive index layer L adjacent to each other is It is preferably set to about 4.0. In this way, it is possible to keep the number of layers of the repetitive layer 32 to the minimum necessary, and to prevent the transmission of blue light (wavelength region: about 430 to 500 nm) from being inhibited. .
Here, the total thickness is 2.0 (0.5λ), 4.0 (1λ), 6.0 (1.5λ). . . . If so, the reflection at λ can be increased. Among these, when the total film thickness is 2.0 (0.5λ), the ratio of (total optical film thickness of high refractive index layer H) / (total optical film thickness of low refractive index layer L) Therefore, it is difficult to increase the reflectivity unless the number of layers of the repeated layer 32 is increased substantially by about 2 times. . Furthermore, the optical film thickness of the low refractive index layer L of the repeating layer becomes extremely thin, and it becomes difficult to form a uniform optical thin film. Further, when the total film thickness is 6.0 (1.5λ), the reflection band (band where the transmittance is approximately 0%) in the wavelength region of about 560 to 600 nm (yellow light), and the reflection band However, the reflection band adjacent to the short wavelength side is too close, and transmission of blue light (wavelength region: about 430 to 500 nm) is inhibited. On the other hand, it is preferable to set the total film thickness to about 4.0 because the number of layers of the repeated layer 32 can be kept to the minimum necessary and the transmission of blue light is not hindered.

The light reduction layer 33 is provided on at least one of the light beam incident side and the light beam emission side of the repeating layer 32, and blue light (wavelength region: about 430 to 500 nm) and green light (wavelength region: about 500) in the transmitted light beam. It is a layer that reduces the amount of transmitted light (˜560 nm). In the present embodiment, the dimming layer 33 is provided on the light beam exit side of the optical multilayer film 3 as shown in FIG. 4, and includes three low-refractive index layers L and three high-refractive index layers. H is alternately stacked.
Such a dimming layer 33 adjusts the optical film thickness of the three low-refractive index layers L and the three high-refractive index layers H as appropriate so that blue light (wavelength region: about 430 to 500 nm) and The transmittance of green light (wavelength region: about 500 to 560 nm) can be set to an arbitrary value. For example, if the optical film thickness of the high refractive index layer H to be added is more than about 1 (when 1 / 4λ (λ = 430 nm) is defined as 1), the transmittance of blue light and green light is greatly reduced. It is possible.
As a specific example, in the light reducing layer 33 shown in FIG. 5, the film thickness of the 39th layer (high refractive index layer H) is 1.18, and the film thickness of the 40th layer (low refractive index layer L) is 0. 86, the film thickness of the 41st layer (high refractive index layer H) is 0.27, the film thickness of the 42nd layer (low refractive index layer L) is 0.52, and the 43rd layer (high refractive index layer H). ) Is 0.12 and the 44th layer (low refractive index layer L) is 1.63. In this case, the transmittance of blue light (wavelength region: about 430 to 500 nm) and green light (wavelength region: about 500 to 560 nm) is 65 to 75%.
32, the 39th layer (high refractive index layer H) has a thickness of 1.30, the 40th layer (low refractive index layer L) has a thickness of 0.79, The film thickness of the 41st layer (high refractive index layer H) is 0.55, the film thickness of the 42nd layer (low refractive index layer L) is 0.68, and the film of the 43rd layer (high refractive index layer H) The thickness is 1.63, and the thickness of the 44th layer (low refractive index layer L) is 1.21. In this case, the transmittance of blue light (wavelength region: about 430 to 500 nm) and green light (wavelength region: about 500 to 560 nm) is 45 to 55%.

The relationship between the light transmittance of the optical multilayer film 3 and the wavelength region of the light flux is as shown in FIG. 6, for example.
In FIG. 6, the transmittance of yellow light (wavelength region: about 560 to 600 nm) is substantially 0%. The transmittance of red light (wavelength region: about 640 nm to 810 nm) is about 100%. The transmittance of blue light (wavelength region: about 430 to 500 nm) and green light (wavelength region: about 500 to 560 nm) is 65 to 75%. Furthermore, the variation (ripple) in the transmittance of blue light and red light is small.

[3. Projector configuration)
The optical multilayer film 1 as described above is used for the cross dichroic prism 444 of the projector 4.
As shown in FIG. 7, the projector 4 includes an integrator illumination optical device 41, a color separation optical device 42, a relay optical system 43, an optical device 44, and a projection lens 45.
The integrator illumination optical device 41 is for illuminating an image forming area of a liquid crystal panel, which will be described later, constituting the optical device 44 substantially uniformly. The integrator illumination optical device 41 includes a light source device 411, a first lens array 412, a second lens array 413, a polarization conversion element 414, a superimposing lens 415, and a reflection mirror 419.

The light source device 411 includes a light source lamp 416 that emits a radial light beam and a reflector 417 that reflects the emitted light emitted from the light source lamp 416. As the light source lamp 416, a halogen lamp, a metal halide lamp, or a high-pressure mercury lamp is frequently used. In FIG. 7, a parabolic mirror is used as the reflector 417. However, the reflector 417 is not limited to this. The reflector 417 is configured by an elliptical mirror, and a light beam reflected by the elliptical mirror on the light beam emission side is converted into parallel light. It is good also as a structure which employ | adopted the collimated concave lens as follows.
The first lens array 412 has a configuration in which small lenses having a substantially rectangular outline when viewed from the optical axis direction are arranged in a matrix. Each small lens splits the light beam emitted from the light source device 411 into a plurality of partial light beams.
The second lens array 413 has substantially the same configuration as the first lens array 412, and has a configuration in which small lenses are arranged in a matrix. The second lens array 413 has a function of forming an image of each small lens of the first lens array 412 on a liquid crystal panel (to be described later) of the optical device 44 together with the superimposing lens 415.

The polarization conversion element 414 is disposed between the second lens array 413 and the superimposing lens 415, and converts light from the second lens array 413 into substantially one type of polarized light.
Specifically, each partial light converted into substantially one type of polarized light by the polarization conversion element 414 is finally substantially superimposed on a liquid crystal panel (described later) of the optical device 44 by the superimposing lens 415. In a projector using a liquid crystal panel of a type that modulates polarized light, only one type of polarized light can be used, and therefore approximately half of the light from the light source device 411 that emits randomly polarized light cannot be used. For this reason, by using the polarization conversion element 414, the light emitted from the light source device 411 is converted into substantially one type of polarized light, and the light use efficiency in the optical device 44 is increased.

The reflection mirror 419 functions as a notch filter that reflects yellow light from the light beam emitted from the light source device 411 and transmits blue light, green light, and red light. The reflection mirror 419 also functions as an ND filter that reduces blue light and green light with an arbitrary transmittance and transmits the light.
Specifically, the reflection mirror 419 includes a flat glass substrate (not shown) and the optical multilayer film 3 formed on the surface of at least one of the light beam incident side and the light beam emission side of the substrate. And is arranged between the light source device 411 and the first lens array 412.
Thereby, in the light flux after passing through the reflection mirror 419, narrow-band yellow light (wavelength region: about 560 to 600 nm) that causes a reduction in image contrast is removed, and green light with a large amount of light (wavelength region: about 500). ˜560 nm) and blue light (wavelength region: about 430 to 500 nm) are dimmed and red light with a small amount of light (wavelength region: about 640 to 810 nm) can be transmitted to the maximum extent.
Such a reflection mirror 419 is preferably arranged in a state orthogonal to the incident light beam. Thereby, it becomes possible to reliably reflect yellow light in a narrow band having a wavelength region of about 560 to 600 nm (wavelength width of about 30 to 40 nm). If the reflection mirror 419 is arranged in a state not orthogonal to the incident light beam, the reflection band is shifted to the green light side, and there is a possibility that a part of yellow light is mixed in the red light.

The color separation optical device 42 includes two dichroic mirrors 421 and 422 and a reflection mirror 423, and a plurality of partial light beams emitted from the integrator illumination optical device 41 by the dichroic mirrors 421 and 422 are converted into red, green, and blue. It has a function of separating into three color lights.
The relay optical system 43 includes an incident side lens 431, a relay lens 433, and reflection mirrors 432 and 434, and guides the green light separated by the color separation optical device 42 to a later-described green light liquid crystal panel of the optical device 44. It has a function.

  At this time, the dichroic mirror 421 of the color separation optical device 42 reflects red light of the light beam emitted from the integrator illumination optical device 41 and transmits blue light and green light. The red light reflected by the dichroic mirror 421 is reflected by the reflection mirror 423, passes through the field lens 418, and reaches a later-described red light liquid crystal panel of the optical device 44. The field lens 418 converts each partial light emitted from the second lens array 413 into a light beam parallel to the central axis (principal ray). The same applies to the field lens 418 provided on the light incident side of the other liquid crystal panel for green light and blue light.

  Of the blue light and green light transmitted through the dichroic mirror 421, the blue light is reflected by the dichroic mirror 422, passes through the field lens 418, and reaches a later-described liquid crystal panel for blue light of the optical device 44. On the other hand, the green light passes through the dichroic mirror 422, passes through the relay optical system 43, and further passes through the field lens 418 to reach a later-described green light liquid crystal panel of the optical device 44. The reason why the relay optical system 43 is used for green light is that the amount of green light is larger than that of other color lights.

The optical device 44 modulates an incident light beam according to image information to form a color image. The optical device 44 includes a liquid crystal panel 441 as a light modulation device to be illuminated (441 R for a red light liquid crystal panel, 441 G for a green light liquid crystal panel, and 441 B for a blue light liquid crystal panel), and And a cross dichroic prism (color synthesis optical element) 444. An incident-side polarizing plate 442 is interposed between the field lens 418 and the liquid crystal panels 441R, 441G, 441B, and between the liquid crystal panels 441 (441R, 441G, 441B) and the cross dichroic prism 444 An exit-side polarizing plate 443 is interposed, and the incident-side polarizing plate 442, the liquid crystal panel 441 (441R, 441G, 441B), and the exit-side polarizing plate 443 perform light modulation of each color light incident thereon.
The liquid crystal panel 441 (441R, 441G, 441B) is a pair of transparent glass substrates in which a liquid crystal as an electro-optical material is hermetically sealed. For example, a polysilicon TFT is used as a switching element in accordance with a given image signal. The polarization direction of the polarized light beam emitted from the incident side polarizing plate 442 is modulated.

  The cross dichroic prism 444 is an optical element that synthesizes an optical image modulated for each color light emitted from the emission-side polarizing plate 443 to form a color image. The cross dichroic prism 444 includes a prism assembly 444E including four triangular prisms 444A to 444D having two orthogonal side surfaces, and is formed in a substantially X-shape formed when the triangular prisms 444A to 444D are bonded together. At the interface, a pair of optical multilayer films 1 and 2 are formed so as to intersect each other.

The prism aggregate 444E is configured by bonding two orthogonal side surfaces of the triangular prisms 444A to 444D to each other, and has a substantially square planar shape.
Of the pair of optical multilayer films 1 and 2, one optical multilayer film 1 is divided and formed on one side surface of the pair of triangular prisms 444A and 444B, respectively. The optical multilayer film 1 is formed so that the first layer of the optical multilayer film 1 is positioned on the triangular prisms 444A and 444B side.
The other optical multilayer film 2 is also divided and formed on the other side surface of the triangular prism 444A and one side surface of the triangular prism 444D, respectively.
The other optical multilayer film 2 reflects red light and transmits blue light and green light.

By these optical multilayer films 1 and 2, the red light and the green light are bent and aligned with the traveling direction of the blue light, so that the three color lights are synthesized.
Examples of a method for forming these optical multilayer films 1 and 2 include a vacuum deposition method, an ion plating method, and a sputtering method.
The color image emitted from the cross dichroic prism 444 is enlarged and projected by the projection lens 45 to form a large screen image on a screen (not shown).

[4. Effects of the embodiment
Therefore, according to this embodiment, the following effects can be produced.
(4-1) In the repeating layer 12 of the optical multilayer film 1, the high refractive index layer H and the low refractive index layer L are alternately arranged, and 3.0 ≦ (the high refractive index layer in the repeating layer 12) The sum of the optical film thicknesses of H / (the sum of the optical film thicknesses of the low refractive index layers L in the repeating layer 12) ≦ 6.0.
Thus, (the sum of the optical film thickness of the high refractive index layer H in the repeating layer 12) / (the sum of the optical film thickness of the low refractive index layer L in the repeating layer 12) is 3.0 or more and 6.0. By setting it as below, the wavelength range of the light which the optical multilayer film 1 reflects can be 500 nm or more and 600 nm or less, and green light can be reflected reliably.
Further, (the total optical film thickness of the high refractive index layer H in the repeating layer 12) / (total optical film thickness of the low refractive index layer L in the repeating layer 12) is 3.0 or more and 6.0 or less. Thus, the optical multilayer film 1 that can transmit blue light and red light can be obtained.
In the case where (the total optical film thickness of the high refractive index layer H in the repeating layer 12) / (total optical film thickness of the low refractive index layer L in the repeating layer 12) is less than 3.0, There is a possibility that the wavelength region of the reflected light becomes wide and the transmittance of red light is lowered.
Further, when (the total optical film thickness of the high refractive index layer H in the repeating layer 12) / (total optical film thickness of the low refractive index layer L in the repeating layer 12) exceeds 6.0. Since the wavelength region of the reflected light becomes narrow, it becomes difficult to reliably reflect the green light.

(4-2) The optical multilayer film 1 of the present embodiment has an optical film thickness of the low refractive index layer L and an optical film of the high refractive index layer H compared to the repeating layer 12 on the light beam incident side and the light beam emission side. Since the first matching portion 111 of the matching layer 11 having a small difference from the thickness is disposed, it is possible to reliably suppress ripples (transmission fluctuations) of red light and blue light.

(4-3) In the repeating layer 12 of the optical multilayer film 1, 3.0 ≦ (total optical film thickness of the high refractive index layer in the repeating layer 12) / (optical film of the low refractive index layer in the repeating layer 12) While maintaining (total thickness) ≦ 6.0, the optical film thickness of the high refractive index layer H is decreased toward the center of the thickness width of the repeating layer 12, and the optical film thickness of the low refractive index layer L is increased. ing.
By configuring the repeating layer 12 with such a configuration, it is possible to more reliably prevent red light and blue light ripples (transmission fluctuations), and to reliably increase the red light and blue light transmittances. Can do.
In order to reliably prevent red light and blue light ripples (transmission fluctuations), there is a method of increasing the number of high refractive index layers and low refractive index layers of the matching layer. There is a possibility that the number of films to be formed increases and the manufacturing efficiency of the optical multilayer film is lowered.
In this embodiment, by adjusting the optical film thickness of the high refractive index layer H and the optical film thickness of the low refractive index layer L in the repetitive layer 12, red light and blue light ripples (transmission fluctuations) are prevented. Therefore, it is not necessary to increase the number of films of the matching layer 11, and a decrease in the manufacturing efficiency of the optical multilayer film 1 can be prevented.

(4-4) The optical thickness of the high refractive index layer H of the second matching portion 112 disposed between the first matching portion 111 of the matching layer 11 and the repeating layer 12 is set to the first matching portion 111. The dimension between the optical film thickness of the high refractive index layer H and the optical film thickness of the high refractive index layer H closest to the second matching portion 112 of the repeating layer 12, and The optical film thickness of the low refractive index layer L is equal to the optical film thickness of the low refractive index layer L of the first matching portion 111 and the optical film of the low refractive index layer L closest to the second matching portion 112 of the repeating layer 12. Since the dimension is between the thickness, reflection of light between the first matching portion 111 and the repeated layer 12 can be prevented.

(4-5) If the number of films constituting the repetitive layer 12 is less than 16, the green light transmittance is increased, and the green light may not be reliably reflected.
On the other hand, in this embodiment, since the number of high refractive index layers H and low refractive index layers L constituting the repeating layer 12 is 8 or more (for example, 10 layers), such a problem occurs. And green light can be reliably reflected.

(4-6) Since Ta ₂ O ₅ is used for the high refractive index layer H, the blue light can be prevented from being absorbed by the high refractive index layer H.
Furthermore, since SiO ₂ is used for the low refractive index layer L and SiO ₂ is relatively inexpensive, the cost of the low refractive index layer L can be reduced.

(4-7) In the projector 4, since the green light is introduced into the relay optical system 43, the optical path becomes longer than other color lights, and the light quantity loss of the green light increases. However, since green light has a larger amount of light than other color lights, even if the light amount loss increases, it is possible to balance with other color lights. Thereby, the projector 4 can form a projection image with good color balance.

(4-8) In the repeating layer 32 of the optical multilayer film 3, the high refractive index layer H and the low refractive index layer L are alternately arranged, and further 10 ≦ (the high refractive index layer H in the repeating layer 32 The sum of the optical film thicknesses) / (the sum of the optical film thicknesses of the low refractive index layers L in the repeating layer 32) ≦ 30.
Thus, (total sum of optical film thickness of high refractive index layer H in repeating layer 32) / (total sum of optical film thickness of low refractive index layer L in repeating layer 32) is 10 or more and 30 or less. The wavelength region of light reflected by the optical multilayer film 3 can be set to about 560 nm to 600 nm, and yellow light in a narrow band can be reliably reflected.
Moreover, blue light ((total sum of optical film thickness of high refractive index layer in repeating layer 32) / (total sum of optical film thickness of low refractive index layer in repeating layer 32) is 10 or more and 30 or less. Wavelength region: about 430 to 500 nm), green light (wavelength region: about 500 to 560 nm), and red light (wavelength region: about 640 to 810 nm) can be made into an optical multilayer film 3 that can transmit with high transmittance. it can.
When (total of optical film thickness of high refractive index layer in repeating layer 32) / (total of optical film thickness of low refractive index layer in repeating layer 32) is less than 10, the reflection region is green light. There is a possibility that the required amount of green light cannot be secured.
On the other hand, when (total of optical film thickness of high refractive index layer in repeating layer 32) / (total of optical film thickness of low refractive index layer in repeating layer 32) exceeds 30, a specific wavelength As a result, the light transmittance of the light is improved and cannot be reflected well, and the undulation (ripple) of the transmission loss of red light and blue light may increase.

(4-9) The optical multilayer film 3 has an optical film thickness of the low refractive index layer L and an optical film of the high refractive index layer H compared to the repetitive layer 32 on at least one of the light beam incident side and the light beam exit side. Since the first matching portion 311 of the matching layer 31 having a small difference from the film thickness is disposed, it is possible to reliably suppress the ripple (transmission fluctuation) of red light and blue light.

(4-10) In the repeating layer 32 of the optical multilayer film 3, 10 ≦ (total of the optical film thickness of the high refractive index layer in the repeating layer 32) / (optical film thickness of the low refractive index layer in the repeating layer 32) While maintaining (total) ≦ 30, the optical film thickness of the high refractive index layer H is decreased toward the center of the thickness width of the repeated layer 32 and the optical film thickness of the low refractive index layer L is increased.
By adopting such a configuration of the repeating layer 32, it is possible to more reliably prevent red light and blue light ripples (transmission fluctuations), and to reliably increase the red light and blue light transmittances. Can do.
In order to reliably prevent red light and blue light ripples (transmission fluctuations), there is a method of increasing the number of high refractive index layers and low refractive index layers of the matching layer. There is a possibility that the number of films to be formed increases and the manufacturing efficiency of the optical multilayer film is lowered.
In the present embodiment, by adjusting the optical film thickness of the high refractive index layer H and the optical film thickness of the low refractive index layer L in the repeating layer 32, ripples of red light and blue light (transmission fluctuation) are prevented. Therefore, it is not necessary to increase the number of films of the matching layer 31, and a decrease in manufacturing efficiency of the optical multilayer film 3 can be prevented.

(4-11) The optical thickness of the high refractive index layer H of the second matching portion 312 disposed between the first matching portion 311 and the repeating layer 32 of the matching layer 31 is set to the first matching portion 311. The dimension between the optical thickness of the high refractive index layer H and the optical thickness of the high refractive index layer H closest to the second matching portion 312 of the repeating layer 32, and the second matching portion 312 The optical film thickness of the low refractive index layer L is equal to the optical film thickness of the low refractive index layer L of the first matching portion 311 and the optical film of the low refractive index layer L closest to the second matching portion 312 of the repeating layer 32. Since the dimension is between the thickness, reflection of light between the first matching portion 311 and the repeated layer 32 can be prevented.

(4-12) If the number of films constituting the repetitive layer 32 is less than 15, respectively, the transmittance of yellow light increases, and there is a possibility that yellow light cannot be reliably reflected.
On the other hand, in the present invention, since the number of high refractive index layers and low refractive index layers constituting the repeating layer 32 is 15 or more, such a problem does not occur.

(4-13) In the repeating layer 32, 1 / 4λ (λ = 430 nm) is defined as 1, and the optical film thickness of the high refractive index layer H and the optical film thickness of the low refractive index layer L that are adjacent to each other. The total is set to about 4.0.
Thereby, the number of layers of the repeating layer 32 can be kept to the minimum necessary level, and the transmission of blue light (wavelength region: about 430 to 500 nm) can be prevented from being inhibited.

(4-14) The high refractive index layer H and the low refractive index layer L are alternately stacked on at least one of the light flux incident side and the light flux exit side of the repeating layer 32, and blue light and green light in the transmitted light flux A light reducing layer 33 for reducing the amount of transmitted light is provided.
Thereby, the optical multilayer film 3 can reflect yellow light in a narrow band (wavelength region: about 560 to 600 nm) and can transmit red light with high transmittance. Furthermore, blue light and green light can be reduced and transmitted with an arbitrary transmittance. Therefore, the single optical multilayer film 3 functions as a reflection mirror that reflects yellow light and transmits blue light, green light, and red light, and attenuates blue light and green light at an arbitrary transmittance. Thus, two functions, that is, a function as an ND filter that transmits light can be expressed. And if the optical film thickness of each of the high refractive index layer H and the low refractive index layer L of the light reducing layer 33 is appropriately adjusted, the transmittance of the blue light and the green light can be arbitrarily set. The amount of light can be adjusted easily and suitably.

(4-15) The high refractive index layer H in each of the repeating layer 32, the matching layer 31, and the light reducing layer 33 preferably contains Nb ₂ O ₅ , and the low refractive index layer L preferably contains SiO _2. .
Thereby, by using Nb ₂ O ₅ for the high refractive index layer H, it is possible to suppress the blue light from being absorbed by the high refractive index layer H.
Moreover, by using SiO ₂ for the low refractive index layer L, the cost of the low refractive index layer L can be reduced.

(4-16) In the reflection mirror 419, the optical multilayer film 3 reflects yellow light and can transmit blue light, green light and red light with high efficiency. In addition, yellow light can be prevented from being mixed. For this reason, since the projector 4 includes the reflection mirror 419, yellow light can be removed from the light flux from the light source device 411. Therefore, the color reproducibility and contrast of the projection image enlarged and projected by the projection lens 45 are improved. be able to.

[5. Modification of Embodiment]
It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the above-described embodiment, the optical multilayer film 1 is used for the cross dichroic prism 444. However, the present invention is not limited to this. For example, the optical multilayer film 1 may be used for a dichroic mirror as an optical element. Furthermore, the optical multilayer film may be used for other optical elements.
In the above embodiment, the cross dichroic prism 444 having the optical multilayer film 1 is mounted on the front type projector 4 that projects from the direction of observing the screen. You may mount in the rear type projector which projects from the opposite side.
Furthermore, not only the projector but also other optical devices may be equipped with the cross dichroic prism 444 or the optical element having the optical multilayer film of the present invention.

In the above-described embodiment, the optical multilayer film 3 is used for the reflection mirror 419 of the projector 4. However, the present invention is not limited thereto, and may be used for a reflection mirror in other display devices and optical devices.
In the above embodiment, the reflection mirror 419 including the optical multilayer film 3 is disposed between the light source device 411 and the first lens array 412, but the present invention is not limited to this. That is, the reflection mirror including the optical multilayer film 3 is installed for at least one of the light flux before being split by the color separation optical device 42 and the light flux after being synthesized by the cross dichroic prism 444. For example, it may be disposed between the cross dichroic prism 444 and the projection lens 45. Further, the optical multilayer film 3 may be formed on the small lenses of the first lens array 412 and the second lens array 413 without providing the reflection mirror 419 itself. Even in these cases, yellow light can be removed from the light source device 411 and the color reproducibility and image contrast projected on the screen can be improved, as in the above embodiment.

Moreover, in the said embodiment, although the number of the high refractive index layers H and the low refractive index layers L which comprise the repeating layer 12 was each 8 or more layers, you may be less than 8 layers. By making the number of repeating layers less than 8 each, the production efficiency of the repeating layers can be increased.
In the embodiment, in the repeating layer 12, the optical film thickness of the high refractive index layer H becomes thinner toward the center of the thickness width of the repeating layer 12, and the optical film thickness of the low refractive index layer L is the thickness of the repeating layer 12. In the vicinity of the portion adjacent to the second matching portion 112 of the matching layer 11 of the repeating layer 12, the optical thickness of the high refractive index layer H / (low refractive index layer). (Optical film thickness of L) is about 6.0, and (optical film thickness of high refractive index layer H) / (optical film thickness of low refractive index layer L) is 5 at the central portion of the thickness width of repeating layer 12. Although it is said that it is about 0.0, it is not restricted to this. In the vicinity of the portion of the matching layer 11 adjacent to the second matching portion 112 of the repeating layer 12, (optical film thickness of the high refractive index layer H) / (optical film thickness of the low refractive index layer L) is about 6.0. Yes, at the center of the thickness width of the repeating layer 12, (optical film thickness of the high refractive index layer H) / (optical film thickness of the low refractive index layer L) may be about 4.0. That is, the relationship between the optical film thickness of the high refractive index layer H in the repeating layer 12 and the optical film thickness of the low refractive index layer L is 3.0 ≦ (the optical film thickness of the high refractive index layer H in the repeating layer 12). ) / (Sum of optical film thicknesses of the low refractive index layer L in the repeating layer 12) ≦ 6.0.

Moreover, in the said embodiment, although the number of the high refractive index layers H and the low refractive index layers L which comprise the repeating layer 32 was each 15 layers or more, it may be less than 15 layers. By making the number of repeating layers less than 15 each, the production efficiency of the repeating layer 32 can be increased.
In the embodiment, the optical film thickness of the high refractive index layer H in the repeating layer 32 becomes thinner toward the center of the thickness width of the repeating layer 32, and the optical film thickness of the low refractive index layer L is the thickness of the repeating layer 32. Assuming that the thickness is increased toward the center of the width, (the optical film thickness of the high refractive index layer H) / (the optical film thickness of the low refractive index layer L) is approximately 26 on the end side in the thickness width direction of the repeating layer 32. In the central portion of the thickness width of the repeating layer 32, (optical film thickness of the high refractive index layer H) / (optical film thickness of the low refractive index layer L) is about 15.3. However, it is not limited to this. For example, (the optical film thickness of the high refractive index layer H) / (the optical film thickness of the low refractive index layer L) is about 30 on the thickness width direction end portion side of the repeating layer 32, and the thickness width of the repeating layer 32 is In the central portion, (optical film thickness of high refractive index layer H) / (optical film thickness of low refractive index layer L) may be about 10. That is, the relationship between the optical film thickness of the high refractive index layer H in the repeating layer 32 and the optical film thickness of the low refractive index layer L is 10 ≦ (total of the optical film thicknesses of the high refractive index layer H in the repeating layer 32. ) / (Sum of optical film thicknesses of the low refractive index layer L in the repeating layer 32) ≦ 30, it is optional.

  Further, in the above embodiment, in the repeating layers 12 and 32, the optical film thickness of the high refractive index layer H decreases toward the center of the thickness width of the layer, and the optical film thickness of the low refractive index layer L increases. However, the present invention is not limited to this, and in the repeating layer, the optical film thickness of the high refractive index layer H and the optical film thickness of the low refractive index layer L may be fixed to a constant value without changing. In this case, it is preferable to appropriately adjust the total number of the high refractive index layer H and the low refractive index layer L of the matching layer to prevent variation in transmittance of red light and blue light.

In the above embodiment, the optical multilayer film 1 has the pair of matching layers 11. However, the present invention is not limited to this, and the optical multilayer film 1 may have only one matching layer of the pair of matching layers. For example, the matching layer may not be disposed only on the light emission side of the optical multilayer film.
By doing in this way, the structure of an optical multilayer film is simplified and the effort concerning manufacture of an optical multilayer film can be saved.

In the above embodiment, the optical multilayer film 3 is configured by sequentially laminating the matching layer 31, the repeating layer 32, and the light reducing layer 33. However, the present invention is not limited to this. That is, for example, the light reduction layer 33 may not be provided. In this case, the optical multilayer film 3 does not have a function as an ND filter, but reflects yellow light and reflects blue light, green light, and red light. It has a function as a notch filter that transmits light, and the manufacturing cost of the optical multilayer film 3 can be reduced by the amount that the light reducing layer 33 is not formed.
Further, the dimming layer 33 may be provided on both sides of the repeating layer 32. In this case, the transmittance of blue light and green light can be adjusted by the pair of light reducing layers, respectively, so that the range of adjustment is widened.
Furthermore, the matching layer 31 and the light reducing layer 33 may be provided on the same surface side of the repeating layer 32. For example, the optical multilayer film includes a repeating layer 32, a pair of matching layers 31 formed on both surfaces of the repeating layer 32, and one or a pair of light reducing layers 33 formed on the matching layer 31. It is good also as a structure. Even in such a configuration, the optical multilayer film functions as an ND filter and a notch filter, as in the above embodiment.

  Next, examples of the present invention will be described.

[6. Regarding the effect of repeating layers in the optical multilayer film 1]
First, in order to confirm the effect of the repeating layer 12 of the optical multilayer film 1 (see FIG. 1) in the above embodiment, the following experiment was performed.
(Example 1-1)
An optical multilayer film having a repeating layer and a pair of matching layers that can be used as the optical multilayer film 1 (see FIG. 1) in the above embodiment was manufactured.
Each of the high refractive index layer and the low refractive index layer in the repeating layer was 10 layers. Further, (the sum of the optical film thicknesses of the high refractive index layer H) / (the sum of the optical film thicknesses of the low refractive index layer L) in the repeating layer is fixed at 5, and both ends (light beam incident side, light beam emission) of the repeating layer are fixed. A matching layer is arranged on each side.
Each of the pair of matching layers has a first matching portion and a second matching portion. Of the matching layers, the first matching portion has one high refractive index layer and one low refractive index layer, and the second matching portion has one high refractive index layer and one low refractive index layer. Each of the high refractive index layer and the low refractive index layer of the optical multilayer film is 14 layers.
Further, Ta ₂ O ₅ was used as the material of the high refractive index layer H of the optical multilayer film, and SiO ₂ was used as the material of the low refractive index layer L.

FIG. 8 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
Such an optical multilayer film has high transmittance of blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 nm to 810 nm), and transmits green light (wavelength region: about 500 to 600 nm). The rate is approximately 0%.

(Example 1-2)
In addition, an optical multilayer film having a repetitive layer and a matching layer that can be used as the optical multilayer film 1 (see FIG. 1) in the above embodiment was manufactured. The structure of this optical multilayer film is as shown in Table 1.

Further, as the material for the high refractive index layer H of the optical multilayer film, Ta ₂ O ₅ was used as in the case of Example 1-1, and as the material for the low refractive index layer L, SiO ₂ was used.

FIG. 9 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
Such an optical multilayer film has high transmittance of blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 nm to 810 nm), and transmits green light (wavelength region: about 500 to 600 nm). The rate is approximately 0%.
Compared with the optical multilayer film of Example 1, the variation in transmittance of blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 nm to 810 nm) is very small.

[7. reference〕
(7-1. Ratio of optical film thickness of high refractive index layer to low refractive index layer in repetitive layer)
In the repetitive layer 12 of the optical multilayer film 1 (see FIG. 1) in the above embodiment, a study was made regarding the ratio between the optical film thickness of the high refractive index layer and the optical film thickness of the low refractive index layer.

(Reference Example 1-1)
An optical multilayer film having no matching layer and only a repeating layer was formed.
The high refractive index layer and the low refractive index layer in the repeating layer of the optical multilayer film are each 10 layers.
The optical film thickness of the high refractive index layer and the optical film thickness of the low refractive index layer in the repeating layer are 1.85 (1 / 4λ (λ = 430 nm) is defined as 1), and (the optical film of the high refractive index layer H) (Total thickness) / (total optical film thickness of low refractive index layer L) was fixed at 1. As a material for the high refractive index layer H, Ta ₂ O ₅ was used, and as a material for the low refractive index layer L, SiO ₂ was used.

FIG. 10 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
In such an optical multilayer film, it was confirmed that the wavelength region of the reflected light beam was too wide and reflected red light in addition to green light.

(Reference Example 1-2)
An optical multilayer film having no matching layer and only a repeating layer was formed.
The high refractive index layer and the low refractive index layer in the repeating layer of the optical multilayer film are each 10 layers.
The optical film thickness of the high-refractive index layer and the optical film thickness of the low-refractive index layer in the repeating layer are set to 5 (1 / 4λ (λ = 430 nm) is defined as 1), and (the optical film thickness of the high-refractive index layer H is (Total) / (total optical film thickness of low refractive index layer L) was fixed at 1. As a material for the high refractive index layer H, Ta ₂ O ₅ was used, and as a material for the low refractive index layer L, SiO ₂ was used.

FIG. 11 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
In such an optical multilayer film, it was confirmed that the wavelength region to be reflected was too narrow to sufficiently reflect green light.
In addition, since the optical film thickness of the high refractive index layer and the optical film thickness of the low refractive index layer in the repeating layer are set to 5, the thickness width of the repeating layer is very thick.

(Reference Example 1-3)
An optical multilayer film having no matching layer and only a repeating layer was formed.
The high refractive index layer and the low refractive index layer in the repeating layer of the optical multilayer film are each 10 layers.
The optical film thickness of the high refractive index layer in the repeating layer is 4.3, and the optical film thickness of the low refractive index layer is 2.15 (1 / 4λ (λ = 430 nm) is defined as 1). The sum of the optical thicknesses of H) / (the sum of the optical thicknesses of the low refractive index layers L) was fixed at 2. As a material for the high refractive index layer H, Ta ₂ O ₅ was used, and as a material for the low refractive index layer L, SiO ₂ was used.

FIG. 12 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
In such an optical multilayer film, it was confirmed that the wavelength region of the reflected light beam was too wide.

(Reference Example 1-4)
An optical multilayer film having no matching layer and only a repeating layer was formed.
The high refractive index layer and the low refractive index layer in the repeating layer of the optical multilayer film are each 10 layers.
The optical film thickness of the high refractive index layer in the repeating layer is 4.74, and the optical film thickness of the low refractive index layer is 1.58 (1 / 4λ (λ = 430 nm) is defined as 1). The sum of the optical thicknesses of H) / (the sum of the optical thicknesses of the low refractive index layers L) was fixed at 3. As a material for the high refractive index layer H, Ta ₂ O ₅ was used, and as a material for the low refractive index layer L, SiO ₂ was used.

FIG. 13 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
Such an optical multilayer film has high transmittance of blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 nm to 810 nm), and transmits green light (wavelength region: about 500 to 600 nm). The rate is approximately 0%.

(Reference Example 1-5)
An optical multilayer film having no matching layer and only a repeating layer was formed.
The high refractive index layer and the low refractive index layer in the repeating layer of the optical multilayer film are each 10 layers.
The optical film thickness of the high refractive index layer in the repetitive layer is 4.92, and the optical film thickness of the low refractive index layer is 1.23 (1 / 4λ (λ = 430 nm) is defined as 1). The total of the optical film thickness of H) / (the total of the optical film thickness of the low refractive index layer L) was fixed at 4. As a material for the high refractive index layer H, Ta ₂ O ₅ was used, and as a material for the low refractive index layer L, SiO ₂ was used.

FIG. 14 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
Such an optical multilayer film has high transmittance of blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 nm to 810 nm), and transmits green light (wavelength region: about 500 to 600 nm). The rate is approximately 0%.

(Reference Example 1-6)
An optical multilayer film having no matching layer and only a repeating layer was formed.
The high refractive index layer and the low refractive index layer in the repeating layer of the optical multilayer film are each 10 layers.
The optical film thickness of the high refractive index layer in the repeating layer is 5 and the optical film thickness of the low refractive index layer is 1 (1 / 4λ (λ = 430 nm) is defined as 1). (Total thickness) / (total optical film thickness of low refractive index layer L) was fixed at 5. As a material for the high refractive index layer H, Ta ₂ O ₅ was used, and as a material for the low refractive index layer L, SiO ₂ was used.

FIG. 15 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
Such an optical multilayer film has high transmittance of blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 nm to 810 nm), and transmits green light (wavelength region: about 500 to 600 nm). The rate is approximately 0%.

(Reference Example 1-7)
An optical multilayer film having no matching layer and only a repeating layer was formed.
The high refractive index layer and the low refractive index layer in the repeating layer of the optical multilayer film are each 10 layers.
The optical film thickness of the high refractive index layer in the repeating layer is 5.1, and the optical film thickness of the low refractive index layer is 0.85 (1 / 4λ (λ = 430 nm) is defined as 1). The sum of the optical film thicknesses of H / (the sum of the optical film thicknesses of the low refractive index layers L) was fixed at 6. As a material for the high refractive index layer H, Ta ₂ O ₅ was used, and as a material for the low refractive index layer L, SiO ₂ was used.

FIG. 16 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
Such an optical multilayer film has high transmittance of blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 nm to 810 nm), and transmits green light (wavelength region: about 500 to 600 nm). The rate is approximately 0%.

(Reference Example 1-8)
An optical multilayer film having no matching layer and only a repeating layer was formed.
The high refractive index layer and the low refractive index layer in the repeating layer of the optical multilayer film are each 10 layers.
The optical film thickness of the high refractive index layer in the repeating layer is 5.25, and the optical film thickness of the low refractive index layer is 0.75 (1 / 4λ (λ = 430 nm) is defined as 1). The total of the optical film thickness of H) / (the total of the optical film thickness of the low refractive index layer L) was fixed at 7. As a material for the high refractive index layer H, Ta ₂ O ₅ was used, and as a material for the low refractive index layer L, SiO ₂ was used.

FIG. 17 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
In such an optical multilayer film, it was confirmed that the wavelength region to be reflected was too narrow to sufficiently reflect green light.

(result)
According to Reference Example 1-1 to Reference Example 1-8 above, in the repeating layer, 3.0 ≦ (total optical film thickness of high refractive index layer H) / (total optical film thickness of low refractive index layer L) By setting ≦ 6.0, the transmittance of blue light (wavelength region: about 430 to 500 nm) and red light (wavelength region: about 640 nm to 810 nm) can be increased, and green light (wavelength region: about It was confirmed that the transmittance of 500 to 600 nm) could be substantially 0%.

(7-2. Total number of high and low refractive index layers in the repeating layer)
(Reference Example 2-1)
An optical multilayer film having no matching layer and only a repeating layer was formed.
The optical film thickness of the high refractive index layer in the repeating layer is 5 and the optical film thickness of the low refractive index layer is 1 (1 / 4λ (λ = 430 nm) is defined as 1). (Total thickness) / (total optical film thickness of low refractive index layer L) was fixed at 5.
There are five high refractive index layers and low refractive index layers in the repeating layer of the optical multilayer film.
As a material for the high refractive index layer H, Ta ₂ O ₅ was used, and as a material for the low refractive index layer L, SiO ₂ was used.

FIG. 18 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
In such an optical multilayer film, blue light and red light are transmitted, and green light is reflected. Although the transmittance of green light is low and the optical multilayer film is suitable for practical use, it is difficult to completely reflect green light.

(Reference Example 2-2)
The same conditions as in Reference Example 2-1 were adopted except that the high refractive index layer and the low refractive index layer in the repeating layer of the optical multilayer film were each 8 layers.
FIG. 19 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
In such an optical multilayer film, blue light and red light are transmitted, and green light is reflected. The transmittance of green light is approximately 0%.

(Reference Example 2-3)
The conditions were the same as in Reference Example 2-1, except that the high refractive index layer and the low refractive index layer in the repeating layer of the optical multilayer film were each 8 layers.
FIG. 20 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
In such an optical multilayer film, blue light and red light are transmitted, and green light is reflected. The transmittance of green light is approximately 0%.

(Reference Example 2-4)
The conditions were the same as in Reference Example 2-1, except that the high refractive index layer and the low refractive index layer in the repeating layer of the optical multilayer film were each 15 layers.
FIG. 21 shows the relationship between the light transmittance of such an optical multilayer film and the wavelength region of the light flux.
In such an optical multilayer film, blue light and red light are transmitted, and green light is reflected. The transmittance of green light is approximately 0%.

(result)
By the above Reference Example 2-1 to Reference Example 2-4, the high-refractive index layer and the low-refractive index layer of the repeating layer are each made to be 8 layers or more, so that the transmittance of green light can be made approximately 0%. I was able to confirm that I could do it.

[8. Regarding the effect of repeating layers in the optical multilayer film 3]
Next, in order to confirm the effect of the repeating layer 32 of the optical multilayer film 3 (see FIG. 4) in the above embodiment, the following experiment was performed.
(Example 2-1)
An optical multilayer film having a repeating layer and a pair of matching layers that can be used as the optical multilayer film 3 in the above embodiment was manufactured. In FIG. 22, the figure which shows the relationship between each layer in the optical multilayer film as Example 2-1, and an optical film thickness was shown.
In FIG. 22, the high refractive index layer and the low refractive index layer of the optical multilayer film are each 21 layers.
Each of the high refractive index layer and the low refractive index layer in the repeating layer was 17 layers. Further, (total sum of optical film thickness of high refractive index layer H) / (total optical film thickness of low refractive index layer L) in the repetitive layer is fixed at 18.7, and both ends (light beam incident side, Matching layers were arranged on the light beam exit side. Then, the optical film thickness of the high refractive index layer is reduced toward the center of the thickness width of the repeated layer, and the optical film thickness of the low refractive index layer is increased (with modulation). Further, the sum of the optical film thicknesses of the high refractive index layer and the low refractive index layer adjacent to each other is defined as 1 / 4λ (λ = 430 nm) as 1, and is set to about 4.
Each of the pair of matching layers has a first matching portion and a second matching portion. Of the matching layers, the first matching portion has one high refractive index layer and one low refractive index layer, and the second matching portion has one high refractive index layer and one low refractive index layer.
Further, Nb ₂ O ₅ was used as the material of the high refractive index layer H of the optical multilayer film, and SiO ₂ was used as the material of the low refractive index layer L.

FIG. 23 shows the relationship between the light transmittance of Example 2-1 (FIG. 22) and the wavelength region of the light flux.
The light transmission experiment to Example 2-1 was performed in the atmosphere, and the incident light was orthogonal to the optical multilayer film.
In FIG. 23, in the optical multilayer film of this example, blue light (wavelength region: about 430 to 500 nm), green light (wavelength region: about 500 to 560 nm) and red light (wavelength region: about 640 to 810 nm) are transmitted. The rate is approximately 100%. The transmittance of yellow light (wavelength region: about 560 to 600 nm) is about 0%, and the wavelength width is about 40 nm. In addition, the variation (ripple) in the transmittance of blue light, green light and red light is very small.

Further, in Example 2-1, the angle between the optical multilayer film and the incident light beam was changed in various ways, and the influence of the incident angle on light transmission was examined. FIG. 24 shows the relationship between the transmittance of the optical multilayer film and the wavelength region when the angle between the optical multilayer film used in Example 2-1 and the incident light beam is variously changed.
In FIG. 24, the solid line indicates the case where the angle is 90 degrees (0-degree incidence), the thick dotted line indicates the case where the angle is 80 degrees (10-degree incidence), and the thin dotted line indicates that the angle is 70 degrees. The case (incident at 20 degrees) is shown. When the angle is 90 degrees, the reflection region (region where the transmittance is approximately 0%) is observed in a short wavelength region of about 400 to 425 nm and a wavelength region (yellow light) of about 560 to 600 nm. . Then, as the angle is tilted, the reflection region shifts to the lower wavelength side, and when incident at 20 degrees, the reflection region is a short wavelength region of about 400 to 420 nm and about 555 to 555. Observed in a wavelength region of 580 nm (yellow light). However, since the shift amount is small, it was found that in Example 2-1, the influence on the light transmission by the incident angle was small.

(Comparative Example 2-1)
As Comparative Example 2-1, an optical multilayer film having a repeating layer and a pair of matching layers was manufactured. In FIG. 25, the figure which shows the relationship between each layer in the optical multilayer film as the comparative example 2-1, and an optical film thickness was shown. The comparative example 2-1 is largely different from the example 2-1 in that the optical film thicknesses of the high refractive index layer and the low refractive index layer are uniform (no modulation) in the thickness width direction of the repeating layer. Different.
In FIG. 25, in this optical multilayer film, the high refractive index layer and the low refractive index layer were each 21 layers.
Each of the high refractive index layer and the low refractive index layer in the repeating layer was 17 layers. The (total sum of the optical film thickness of the high refractive index layer H) / (total sum of the optical film thickness of the low refractive index layer L) in the repeating layer is fixed to 17, and both ends of the repeating layer (light beam incident side, light beam emitting side) A matching layer was disposed in each. In the thickness width direction of the repetitive layer, the optical film thickness of the high refractive index layer was uniformly about 3.75, and the optical film thickness of the low refractive index layer was uniformly about 0.25 (no modulation). As a result, the sum of the optical film thicknesses of the high refractive index layer and the low refractive index layer adjacent to each other is about 4 (1 / 4λ (λ = 430 nm) is defined as 1).
Each of the pair of matching layers has a first matching portion and a second matching portion. Of the matching layers, the first matching portion has one high refractive index layer and one low refractive index layer, and the second matching portion has one high refractive index layer and one low refractive index layer.
Further, Nb ₂ O ₅ was used as the material of the high refractive index layer H of the optical multilayer film, and SiO ₂ was used as the material of the low refractive index layer L.

FIG. 26 shows the relationship between the light transmittance of Comparative Example 2-1 (FIG. 25) and the wavelength region of the light flux.
In FIG. 26, in Comparative Example 2-1, the transmittance of blue light (wavelength region: about 430 to 500 nm), green light (wavelength region: about 500 to 560 nm) and red light (wavelength region: about 640 to 810 nm). The fluctuation (ripple) is remarkable.

(Comparative Example 2-2)
As Comparative Example 2-2, an optical multilayer film having a repeating layer and a pair of matching layers was manufactured. In FIG. 27, the figure which shows the relationship between each layer in the optical multilayer film as Comparative Example 2-2, and an optical film thickness was shown. The comparative example 2-2 is different from the above example 2-1 in the repeating layer (total optical film thickness of the high refractive index layer H) / (total optical film thickness of the low refractive index layer L). Is greatly different in that the value of 1/20 is 1/20.
In FIG. 27, the optical multilayer film has 21 high refractive index layers and 21 low refractive index layers.
Each of the high refractive index layer and the low refractive index layer in the repeating layer was 17 layers. The (total sum of optical film thickness of high refractive index layer H) / (total optical film thickness of low refractive index layer L) in the repetitive layer is fixed to 1/20, and both ends (light beam incident side, light beam emission) of the repetitive layer are fixed. A matching layer is arranged on each side. Then, the optical film thickness of the high refractive index layer is reduced toward the center of the thickness width of the repeated layer, and the optical film thickness of the low refractive index layer is increased (with modulation). Further, the sum of the optical film thicknesses of the high refractive index layer and the low refractive index layer adjacent to each other is set to about 4 (1 / 4λ (λ = 430 nm) is defined as 1).
Each of the pair of matching layers has a first matching portion and a second matching portion. Of the matching layers, the first matching portion has one high refractive index layer and one low refractive index layer, and the second matching portion has one high refractive index layer and one low refractive index layer.
Further, Nb ₂ O ₅ was used as the material of the high refractive index layer H of the optical multilayer film, and SiO ₂ was used as the material of the low refractive index layer L.

FIG. 28 shows the relationship between the light transmittance of Comparative Example 2-2 (FIG. 27) and the wavelength region of the light flux.
28, in Comparative Example 2-2, the transmittances of blue light (wavelength region: about 430 to 500 nm), green light (wavelength region: about 500 to 560 nm), and red light (wavelength region: about 640 nm to 810 nm) are obtained. The transmittance of yellow light (wavelength region: about 560 to 595 nm) is about 0%. In addition, the variation (ripple) in the transmittance of blue light, green light and red light is very small.

In Comparative Example 2-2, the angle between the optical multilayer film and the incident light beam was changed in various ways, and the influence of the incident angle on light transmission was examined. FIG. 29 shows the relationship between the transmittance of the optical multilayer film and the wavelength region when the angle between the optical multilayer film used in Comparative Example 2-2 and the incident light beam is variously changed.
In FIG. 29, the solid line indicates the case where the angle is 90 degrees (0 degree incidence), the thick dotted line indicates the case where the angle is 80 degrees (10 degrees incidence), and the thin dotted line indicates that the angle is 70 degrees. Case (20 degree incidence) is shown. When the angle is 90 degrees, the reflection region (region where the transmittance is approximately 0%) is observed in a short wavelength region of about 400 to 425 nm and a wavelength region (yellow light) of about 560 to 595 nm. . Then, as the angle is inclined, the reflection region is greatly shifted toward the low wavelength side. In the case of 20 ° incidence, the reflection region is a short wavelength region of about 405 nm or less, and about 540 to about 540 nm. Observed in a wavelength region of 575 nm (yellow light). Thus, in Comparative Example 2-2, it was found that the shift amount was significantly larger than that in Example 2-1, and the angle dependency of transmitted light was inferior when the incident angle changed. Therefore, in Comparative Example 2-2, a reflection / transmission effect substantially the same as that of Example 2-1 was obtained, but it was found that the angle dependency of transmitted light was inferior, so that it was not suitable as a reflection mirror.

(result)
By the above Example 2-1 and Comparative Example 2-1, (total of optical film thickness of high refractive index layer H) / (total of optical film thickness of low refractive index layer L) in the repeated layer is 18.7. If so, the transmittance of blue light (wavelength region: about 430 to 500 nm), green light (wavelength region: about 500 to 560 nm) and red light (wavelength region: about 640 to 810 nm) becomes approximately 100%, and yellow light It was found that the transmittance of (wavelength region: about 560 to 590 nm) was approximately 0%. Moreover, blue light (wavelength region: about 430 to 500 nm) is obtained by reducing the optical film thickness of the high refractive index layer toward the center of the thickness width of the repeating layer and increasing the optical film thickness of the low refractive index layer. It was found that the transmittance fluctuation (ripple) of green light (wavelength region: about 500 to 560 nm) and red light (wavelength region: about 640 to 810 nm) can be suppressed small.
Further, according to the above Example 2-1 and Comparative Example 2-2, (the total optical film thickness of the high refractive index layer H) / (total optical film thickness of the low refractive index layer L) in the repeating layer is 18 It was found that an optical multilayer film excellent in the angle dependency of the transmitted light when the incident angle is changed can be obtained by setting.

[9. Regarding the effect of the light reducing layer in the optical multilayer film 3]
Next, in order to confirm the effect of the light reducing layer 33 of the optical multilayer film 3 (see FIG. 7) in the above embodiment, the following experiment was performed.
(Example 2-2)
An optical multilayer film having a repeating layer, a matching layer, and a light reducing layer that can be used as the optical multilayer film 3 (see FIG. 7) in the above embodiment was manufactured. In FIG. 30, the figure which shows the relationship between each layer in the optical multilayer film as Example 2-2 and an optical film thickness was shown.
In FIG. 30, the optical multilayer film has 22 high and low refractive index layers.
Each of the high refractive index layer and the low refractive index layer in the repeating layer was 17 layers. The (total optical film thickness of the high refractive index layer H) / (total optical film thickness of the low refractive index layer L) in the repeating layer was fixed at 18.1. The optical film thickness of the high refractive index layer is decreased toward the center of the thickness width of the repeated layer, and the optical film thickness of the low refractive index layer is increased (with modulation). Further, the sum of the optical film thicknesses of the high refractive index layer and the low refractive index layer adjacent to each other is set to about 4 (1 / 4λ (λ = 430 nm) is defined as 1).
The matching layer is disposed on the light beam incident side of the repeating layer and has a first matching portion and a second matching portion. Of the matching layers, the first matching portion has one high refractive index layer and one low refractive index layer. The second matching portion of the matching layers has one high refractive index layer and one low refractive index layer.
The dimming layer has three high refractive index layers and three low refractive index layers. In the 43rd high refractive index layer, the optical film thickness is about 0.2, and in the 44th low refractive index layer, the optical film thickness is about 1.7 (1 / 4λ (λ = 430 nm) is defined as 1).
Further, Nb ₂ O ₅ was used as the material of the high refractive index layer H of the optical multilayer film, and SiO ₂ was used as the material of the low refractive index layer L.

FIG. 31 shows the relationship between the light transmittance of Example 2-2 (FIG. 30) and the wavelength region of the light flux.
In Example 2-2, the transmittance of red light (wavelength region: about 640 to 810 nm) is approximately 100%. The transmittance of blue light (wavelength region: about 430 to 500 nm) and green light (wavelength region: about 500 to 560 nm) is 65 to 75%. The transmittance of yellow light (wavelength region: about 560 to 590 nm) is about 0%. Further, it can be seen that the transmittance fluctuation (ripple) of blue light (wavelength region: about 430 to 500 nm), green light (wavelength region: about 500 to 560 nm) and red light (wavelength region: about 640 to 810 nm) is small. . Therefore, it was found that Example 2-2 functions as a reflection mirror that reflects only yellow light, and also functions as an ND filter that reduces blue light and green light by 25 to 35%.

(Example 2-3)
An optical multilayer film having a repeating layer, a matching layer, and a light reducing layer that can be used as the optical multilayer film 3 (see FIG. 7) in the above embodiment was manufactured. In FIG. 32, the figure which shows the relationship between each layer in the optical multilayer film as Example 2-3 and an optical film thickness was shown. In addition, Example 2-3 differs from Example 2-2 only in the film thicknesses of the high refractive index layer and the low refractive index layer in the light reduction layer.
In FIG. 32, the optical multilayer film has 22 high and low refractive index layers.
Each of the high refractive index layer and the low refractive index layer in the repeating layer was 17 layers. (Sum of optical film thickness of high refractive index layer H) / (Total of optical film thickness of low refractive index layer L) in the repetitive layer was fixed at 18.2. The optical film thickness of the high refractive index layer is decreased toward the center of the thickness width of the repeated layer, and the optical film thickness of the low refractive index layer is increased (with modulation). Further, the sum of the optical film thicknesses of the high refractive index layer and the low refractive index layer adjacent to each other is set to about 4 (1 / 4λ (λ = 430 nm) is defined as 1).
The matching layer is disposed on the light beam incident side of the repeating layer and has a first matching portion and a second matching portion. Of the matching layers, the first matching portion has one high refractive index layer and one low refractive index layer. The second matching portion of the matching layers has one high refractive index layer and one low refractive index layer.
The dimming layer has three high refractive index layers and three low refractive index layers. The 43th high refractive index layer has an optical film thickness of about 1.7, and the 44th low refractive index layer has an optical film thickness of about 1.2 (1 / 4λ (λ = 430 nm) is defined as 1).
Further, Nb ₂ O ₅ was used as the material of the high refractive index layer H of the optical multilayer film, and SiO ₂ was used as the material of the low refractive index layer L.

FIG. 33 shows the relationship between the light transmittance of Example 2-3 (FIG. 32) and the wavelength region of the light flux.
In Example 2-3, the transmittance of red light (wavelength region: about 640 to 810 nm) is approximately 100%. The transmittances of blue light (wavelength region: about 430 to 500 nm) and green light (wavelength region: about 500 to 560 nm) are 45 to 55%. The transmittance of yellow light (wavelength region: about 560 to 590 nm) is about 0%. Further, it can be seen that the transmittance fluctuation (ripple) of blue light (wavelength region: about 430 to 500 nm), green light (wavelength region: about 500 to 560 nm) and red light (wavelength region: about 640 to 810 nm) is small. . Therefore, it was found that Example 2-3 functions as a reflection mirror that reflects only yellow light, and also functions as an ND filter that reduces blue light and green light by 45 to 55%.

(Comparative Example 2-3)
As Comparative Example 2-3, an optical multilayer film having a repeating layer, a matching layer, and a darkening layer was manufactured. In FIG. 34, the figure which shows the relationship between each layer in the optical multilayer film as Comparative Example 2-3 and an optical film thickness was shown. Comparative Example 2-3 is significantly different from Example 2-2 in that the optical film thicknesses of the high refractive index layer and the low refractive index layer are uniform (no modulation) in the thickness width direction of the repeating layer.
In FIG. 34, the optical multilayer film has 22 high and low refractive index layers.
Each of the high refractive index layer and the low refractive index layer in the repeating layer was 17 layers. (Sum of optical film thickness of high refractive index layer H) / (Total of optical film thickness of low refractive index layer L) in the repeating layer was fixed at 16.7. In the thickness width direction of the repetitive layer, the optical film thickness of the high refractive index layer was uniformly about 3.75, and the optical film thickness of the low refractive index layer was uniformly about 0.25 (no modulation). As a result, the sum of the optical film thicknesses of the high refractive index layer and the low refractive index layer adjacent to each other is about 4 (1 / 4λ (λ = 430 nm) is defined as 1).
The matching layer is disposed on the light beam incident side of the repeating layer and has a first matching portion and a second matching portion. Of the matching layers, the first matching portion has one high refractive index layer and one low refractive index layer. The second matching portion of the matching layers has one high refractive index layer and one low refractive index layer.
The dimming layer has three high refractive index layers and three low refractive index layers. In the 43rd high refractive index layer, the optical film thickness is about 0.2, and in the 44th low refractive index layer, the optical film thickness is about 1.7 (1 / 4λ (λ = 430 nm) is defined as 1).
Further, Nb ₂ O ₅ was used as the material of the high refractive index layer H of the optical multilayer film, and SiO ₂ was used as the material of the low refractive index layer L.

FIG. 35 shows the relationship between the light transmittance of Comparative Example 2-3 (FIG. 34) and the wavelength region of the light flux.
In Comparative Example 2-3, the transmittance of red light (wavelength region: about 640 to 810 nm) is about 100%. The transmittances of blue light (wavelength region: about 430 to 500 nm) and green light (wavelength region: about 500 to 560 nm) are 45 to 55%. The transmittance of yellow light (wavelength region: about 560 to 590 nm) is about 0%.
However, in Example 2-3, it can be seen that the transmittance fluctuation (ripple) of blue light (wavelength region: about 430 to 500 nm) and green light (wavelength region: about 500 to 560 nm) is remarkably large.

(result)
By providing the light reducing layer in the optical multilayer film as shown in FIGS. 30 and 32 according to the above Example 2-1 and Example 2-2, the transmittance of red light (wavelength region: about 640 to 810 nm) The transmittance of blue light (wavelength region: about 430 to 500 nm) and green light (wavelength region: about 500 to 560 nm) can be controlled to 45 to 75%. At the same time, it was found that the transmittance of yellow light (wavelength region: about 560 to 590 nm) can be maintained at substantially 0%.
Moreover, by the above comparative example 2-3, while reducing the optical film thickness of a high refractive index layer toward the center of the thickness width of a repeating layer, and increasing the optical film thickness of a low refractive index layer, it is blue light. (Wavelength region: about 430 to 500 nm), green light (wavelength region: about 500 to 560 nm) and red light (wavelength region: about 640 to 810 nm) transmittance variation (ripple) was found to be able to be suppressed small. .

  The present invention can be used for an optical multilayer film used for an optical element such as a cross dichroic prism or a reflection mirror such as a notch filter.

Sectional drawing which shows the optical multilayer film concerning embodiment of this invention. The figure which shows the relationship between each layer in the said optical multilayer film, and an optical film thickness. The figure which shows the relationship between the transmittance | permeability of the light beam of the said optical multilayer film, and the wavelength range of a light beam. Sectional drawing which shows the optical multilayer film concerning embodiment of this invention. The figure which shows the relationship between each layer in the said optical multilayer film, and an optical film thickness. The figure which shows the relationship between the transmittance | permeability of the light beam of the said optical multilayer film, and the wavelength range of a light beam. FIG. 2 is a schematic diagram showing an optical system of a projector using the optical multilayer film. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Example 1-1, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Example 1-2, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 1-1, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 1-2, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 1-3, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 1-4, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 1-5, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 1-6, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 1-7, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 1-8, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 2-1, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 2-2, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 2-3, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Reference Example 2-4, and a wavelength range. The figure which shows the relationship between each layer in the optical multilayer film used in Example 2-1, and an optical film thickness. FIG. 6 is a diagram showing the relationship between the transmittance of the optical multilayer film used in Example 2-1 and the wavelength region. The figure which shows the relationship between the transmittance | permeability of the said optical multilayer film, and a wavelength area | region at the time of changing variously the angle which the optical multilayer film used in Example 2-1 and an incident light beam make. The figure which shows the relationship between each layer in the optical multilayer film used by Comparative Example 2-1, and an optical film thickness. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Comparative Example 2-1, and a wavelength range. The figure which shows the relationship between each layer in the optical multilayer film used in Comparative Example 2-2, and an optical film thickness. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Comparative Example 2-2, and a wavelength range. The figure which shows the relationship between the transmittance | permeability of the said optical multilayer film, and a wavelength area | region when changing the angle which the optical multilayer film used in Comparative Example 2-2 and the incident light beam variously change. The figure which shows the relationship between each layer in the optical multilayer film used in Example 2-2, and an optical film thickness. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Example 2-2, and a wavelength range. The figure which shows the relationship between each layer in the optical multilayer film used in Example 2-3, and an optical film thickness. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Example 2-3, and a wavelength range. The figure which shows the relationship between each layer in the optical multilayer film used by Comparative Example 2-3, and an optical film thickness. The figure which shows the relationship between the transmittance | permeability of the optical multilayer film used in Comparative Example 2-3, and a wavelength range. FIG. 10 is a schematic diagram showing an optical system of a conventional projector.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical multilayer film, 2 ... Optical multilayer film, 4 ... Projector, 11 ... Matching layer, 12 ... Repeating layer, 45 ... Projection lens (projection optical apparatus), 441 ... Liquid crystal panel (light modulation apparatus), 441R, 441G, 441B ... Liquid crystal panel (light modulation device), 444 ... Cross dichroic prism (color combining optical element), 444E ... Prism assembly, 444A, 444B ... Triangular prism, 444C, 444D ... Triangular prism, H ... High refractive index layer, L ... Low refractive index layer

Claims (12)

In an optical multilayer film in which high refractive index layers and low refractive index layers having different refractive indexes are alternately laminated,
The optical multilayer film is a repeating layer in which high refractive index layers and low refractive index layers having different optical film thicknesses are alternately stacked,
The repetitive layer is disposed on at least one of the light beam entrance side and the light beam exit side to prevent undulation of transmission loss of transmitted light beams of red light and blue light, and a high refractive index layer and a low refractive index layer are provided. Each having one or more matching layers stacked alternately,
The repetitive layer is 3.0 ≦ (sum of the optical film thickness of the high refractive index layer in the repetitive layer) / (sum of the optical film thickness of the low refractive index layer in the repetitive layer) ≦ 30,
An optical multilayer film, wherein the optical film thickness of the high refractive index layer decreases toward the center of the thickness width of the repeating layer, and the optical film thickness of the low refractive index layer increases. The optical multilayer film according to claim 1,
The repeating layer satisfies 3.0 ≦ (total optical film thickness of the high refractive index layer in the repeating layer) / (total optical film thickness of the low refractive index layer in the repeating layer) ≦ 6.0. An optical multilayer film characterized by the above. The optical multilayer film according to claim 1 or 2,
The number of high refractive index layers and low refractive index layers in the repeating layer is 8 or more, respectively. The optical multilayer film according to any one of claims 1 to 3,
The optical multilayer film, wherein the high refractive index layer forming the repeating layer and the matching layer contains Ta ₂ O ₅ , and the low refractive index layer contains SiO ₂ . The optical multilayer film according to claim 1,
The repetitive layer is 10 ≦ (total optical film thickness of the high refractive index layer in the repetitive layer)
/ (Total of optical film thicknesses of the low refractive index layers in the repetitive layer) ≦ 30. The optical multilayer film according to claim 5,
The number of high refractive index layers and low refractive index layers in the repeating layer is 15 or more, respectively. The optical multilayer film according to claim 5 or 6,
In the repeating layer, ¼λ (λ = 430 nm) is defined as 1, and the total of the optical film thickness of the high refractive index layer and the optical film thickness of the low refractive index layer adjacent to each other is 3.8-4. An optical multilayer film characterized by being set to .2 . The optical multilayer film according to any one of claims 5 to 7,
The optical multilayer film, wherein the high refractive index layer contains Nb ₂ O ₅ and the low refractive index layer contains SiO ₂ .   An optical element comprising the optical multilayer film according to claim 1. In a color combining optical element that combines incident red light, blue light, and green light and emits them in a certain direction.
The color synthesizing optical element includes four triangular prisms each having two substantially orthogonal side surfaces, and a prism assembly formed by bonding the two side surfaces of the triangular prisms together.
A pair of optical multilayer films formed between and intersecting the triangular prisms adjacent to each other of the prism assembly,
Of the pair of optical multilayer films, one optical multilayer film is the optical multilayer film according to any one of claims 1 to 4, which reflects green light and transmits red light and blue light.
The other optical multilayer film is another optical multilayer film that reflects either red light or blue light and transmits either red light or blue light and green light. element. A plurality of light modulation devices that modulate the light beam emitted from the light source according to image information for each color light;
A color synthesizing optical element for synthesizing the luminous flux modulated by each light modulator;
A projection optical device that enlarges and projects the color light synthesized by the color synthesis optical element to form a projection image, and a projector comprising:
The projector according to claim 10, wherein the color synthesis optical element is the color synthesis optical element according to claim 10. A flat transparent substrate;
The optical multilayer film according to any one of claims 5 to 8, which is provided on the transparent substrate, reflects yellow light from an incident light beam, and transmits blue light, green light and red light; A reflection mirror characterized by comprising:

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